A breakthrough in the NFL labor stalemate could soon be in the offing.

A league source confirmed last night that a federal judge has told the owners and locked-out players that she will force them to return to mediated talks sometime this week.

Judge Susan Nelson, who is hearing the request by 10 players — including Giants defensive end Osi Umenyiora — for an injunction that would require the owners to lift the lockout, told both sides yesterday that she wants more mediation first.

That’s potentially good news for fans, because the owners — who had yielded a huge amount of ground in mediated talks just before imposing a lockout last month — are thought to be eager to avoid the costly antitrust case being mounted by the 10 players and their decertified union.

The big question now, however, is where that mediation will be held. The owners want the talks to be held again in Washington, D.C., under the supervision of federal mediator George Cohen, while the players are pushing for Nelson to supervise the discussions in her home base of St. Paul, Minn.

The players also want talks in Nelson’s immediate territory because she is viewed as more sympathetic to their case than Cohen — a position she appeared to make clear during the first hearing on the injunction last Wednesday.

Nelson repeatedly stated she felt the players had justification for their antitrust claim. She also peppered the NFL’s lead attorney with nearly 70 questions while at times mocking the owners’ attempt to counter the players with a Depression-era labor statute designed to protect workers.

Soon after that hearing, the owners made a public push for more mediation and even guaranteed the players they would not use a return to the negotiating table against them in court.

The union rejected that plea from the owners almost immediately, no doubt in large part because the players feel the legal winds are firmly at their backs.

But Nelson didn’t give the players much choice after a one-hour conference call with both sides on Friday in which, one source said, she warned them more mediation was coming.